A variety of air launched rockets and missiles have been either produced or proposed for a variety of military and space oriented missions. Such air vehicles are typically stored beneath the wing of an aircraft prior to launch. In order to allow secure storage of the rocket or missile below the aircraft wing without adversely affecting aircraft aerodynamics, the air vehicle control fins must be folded away from the airstream.
Conventional fin fold mechanisms, which may also be referred to as automatic fin deployment mechanisms, have used springs and hydraulic actuators adjacent to the fin to deploy it immediately after rocket or missile launch. Controlled rotation of the deployed fin(s) is generally required for control of the missile or rocket. Deployment mechanisms for such fins tend to be rather large and to produce flight hindering aerodynamic drag. While such mechanisms may be appropriate for relatively low speed air vehicles, they create flight problems for high speed supersonic vehicles such as are now being designed and produced. A further problem with military vehicles of this type is that large fin fold mechanisms increase the radar cross section of the fin and thus increase the likelihood of undesired detection.
An example of the prior art can be found in U.S. Pat. No. 3,563,495 to Korn. In the Korn patent, pneumatic or hydraulic means mounted to a slideable cylinder is positioned in the fin adjacent to a hinge. Sliding actuation of a shaft which is keyed to the hinge causes a raising and lowering of the fin. While the Korn device is an improvement over the prior art, the hinge and its base increase the fin cross section unacceptably. Further, because of its raised hinge, the Korn device forms an aerodynamically objectionable extension from the rocket body even when the fin is retracted.
Another example of prior art can be found in U.S. Pat. No. 2,977,880 to Kershner. The fin erector of Kershner comprises an external spring mechanism mounted on the exterior of the air vehicle. The Kershner device has a great deal of external hardware adjacent to the fin and thus produces a substantial increase in aircraft and missile drag during flight. Further, it is not clear whether the fin of Kershner could be actively controlled (rotated) in a manner suitable for modern missile or rocket control. Another spring loaded fin erection mechanism is shown in U.S. Pat. No. 3,695,556 to Gauzza et al.
In view of the above, a need clearly exists for improved automatic fin deployment mechanisms that produce less aerodynamic drag on high speed air vehicles and have less effect on the cross section of extended fins.
A need also exists for automatically deployed fin fold mechanisms that allow full controlled rotational movement of the extended fins after extension.